Dennis Smith: Thinking About History in Geologic Time May Save Us the Next Time a Tsunami Strikes

[Dennis Smith, a retired New York City firefighter, is the author of the forthcoming "San Francisco Is Burning," a history of the 1906 earthquake.]

SCIENTISTS, like art teachers who have not mastered anatomy or drawing, often assume that what they do not know is not important. And, when it comes to earth science, what they do not know is the pattern of geologic time, particularly what has happened beneath the ground in the 4.5 billion years that we assume the earth has existed. What have been the consequences of large waves and water movement to whatever life existed on its surface?

Humans might know that the universe is theorized to be 15 billion years old, or that the Milky Way was formed 13 billion years ago, but the way we feel about ourselves in relation to a 4.5 billion-year-old earth is not much different from the way indigenous people studying a night sky might have felt about themselves anywhere on earth 10,000 years ago. The subject of what can possibly happen on earth is simply too big for most of us to handle if we are to continue to be an optimistic race. And so we hope for the best.

Yet there are some things we should be thinking about in a more serious manner. There are facts that we should not let pass into an obscure scientific history, for remembering them will undoubtedly help ensure a safer future for all on our planet. This is harder than it sounds.

We have a tsunami warning system in the Pacific Ocean because, in recent history, we've experienced tsunamis there. We don't have a similar system in the Indian Ocean. This has something to do with the technologies developing nations can afford, of course, But it also has to do with the fact that our experience with the giant waves in this region is less immediate. Yet the single worst explosion in our known geologic history - an eruption of a 20-by-60-mile caldera some 71,000 years ago - occurred on Sumatra, just 100 miles from the epicenter of Sunday's earthquake.

The earlier eruption left a 10,000 square-mile sheet of volcanic rock, more than a thousand feet thick, and so filled the sky with ash that it probably created our last ice age. Still, the eastern Indian Ocean is thought to be an area of infrequent tsunami activity. Earthquakes as a rule occur at the ridge of land and water, where plates usually meet and either slide, thrust or pull apart, releasing awesome power. But there are exceptions.

Americans believe that earthquakes are a West Coast problem. But the largest earthquake ever in the United States that we know of, probably at least as large as the one that destroyed most of San Francisco in 1906, occurred in the area of the Mississippi Valley in 1811. Boats were thrown over in the river and people drowned. Whole islands simply disappeared. This earthquake, and its aftershocks a year later, were so destructive that Congress passed the first federal relief act in 1815 to support the farmers whose previously healthy and farmable land was turned to swamp, sand and mud.

The quake covered a much larger area than the San Francisco catastrophe, but fewer people were killed, for in 1811 the area was sparsely settled by fewer than 10,000, most living in log houses that would have sustained the shaking well. However, the seismological activity that caused it has never been explained in definitive terms....

I hope for the future in the same way I hope when I step on to an air-plane. I hope the people in control are of sound mind and body, and that they know what they are doing. Yet I know that simply wishing this is not enough. Terrible events in the future are in-evitable. But I also know that we will continue to be unprepared for them if we don't look more deeply into the past. By this, I don't mean a fire last year or a volcanic eruption a century ago. I mean another past, in geologic time, that we simply don't know enough about. Thinking about that explosion on Sumatra 71,000 years ago is a good place to start.